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Please open the Dell Audio by Realtek, under the main tab ensure there is no check mark on mute for the microphone, under advanced tab select restore defaults and restore. Check the jack information, if the microphone jack is highlighted when you connect. Also request you to please check if the microphone works on another device. If it still does not work please reinstall the Realtek audio drivers using this link http://dell.to/174NXtb (Select the OS and the version).